diff --git a/Eigen/src/Core/arch/AltiVec/MatrixProduct.h b/Eigen/src/Core/arch/AltiVec/MatrixProduct.h
index 52768c5da..dd233b3cb 100644
--- a/Eigen/src/Core/arch/AltiVec/MatrixProduct.h
+++ b/Eigen/src/Core/arch/AltiVec/MatrixProduct.h
@@ -29,7 +29,7 @@
 
 
 // Check if we want to enable dynamic dispatch. Not supported by LLVM.
-if defined(EIGEN_ALTIVEC_ENABLE_MMA_DYNAMIC_DISPATCH) && !EIGEN_COMP_LLVM
+#if defined(EIGEN_ALTIVEC_ENABLE_MMA_DYNAMIC_DISPATCH) && !EIGEN_COMP_LLVM
 #define EIGEN_ALTIVEC_MMA_DYNAMIC_DISPATCH 1
 // Otherwise, use MMA by default if available.
 #elif defined(__MMA__)